In laboratory experiments, they mated worker termites with kings and queens.

All the offspring were raised in exactly the same environment. But each of the different parent combinations resulted in specific mixtures of castes and sexes in their offspring.

"If environment caste determination was true, then we would expect all the offspring from each of the crosses to be the same combinations," Lo says.

Specifically, when the royals mated, they gave rise to workers. But the worker matings, which happen rarely under normal circumstances, appeared to be needed to produce the royals.

It's a very different situation to human royalty, Lo says.

"In the British monarchy, for example, royals give rise to royals, but in the case of the termites you have this kind of symmetry," he says. "The only way you can explain it is by a genetic mechanism."

In the genes

In fact, the results point to a possible gene on the termite X chromosome, which the researchers have dubbed 'worker'.

Like humans, termites have X and Y chromosomes that determine their gender. Females have two X chromosomes, while males have an X and a Y.

"It's really the first step in understanding how caste is determined," Lo says. "Previous to our work, nobody had any idea of how it worked."

Ultimately, scientists could use that new understanding to prevent the damage termites can cause to buildings, Lo says.

"Eventually we hope that we'll be able to find very specific compounds that could make the colony produce a high percentage of royals," he says.

"That would cause a collapse of the colony, because these royals just sit around doing nothing and waiting to be fed. They're pretty much useless when it comes to hard work."